Cnr2 deficiency confers resistance to inflammation-induced preterm birth in mice

Placental Cannabinoid Receptor Expression in Preterm Birth

Background: The cannabinoid receptor (CBR) plays a significant role in oogenesis, pregnancy, and childbirth. It might also play a significant role in preterm birth (PTB). The aim of the study was to investigate the association between the expression of the CBR in the placenta and the incidence of PTB. Methods: This prospective, observational, multicentre preliminary study was conducted on placental samples obtained from 109 women. The study included 95 patients hospitalized due to the high risk of PTB. They were divided into two groups: Group 1, where the expression of the CBR1 and CBR1a was analyzed, and Group 2, in which we examined CBR2 expression. The control group, that is, Group 3, consisted of 14 women who delivered at term, and their placentas were tested for the presence of all three receptor types (CBR1, CBR1a, and CBR2). Results: The study used reverse transcription and real-time PCR methods to assess the expression of CBRs in the placental tissues. The expression of the CBR2, CBR1, and CBR1a receptors was significantly lower in the placentas of women after PTB compared to those after term births, p = 0.038, 0.033, and 0.034, respectively. Conclusions: The presence of CBR mRNA in the human placental tissue was confirmed. The decreased expression of CBRs could serve as an indicator in predicting PTB.

Nanoplastic impact on bone microenvironment: A snapshot from murine bone cells

Our world is made of plastic. Plastic waste deeply affects our health entering the food chain. The degradation and/or fragmentation of plastics due to weathering processes result in the generation of nanoplastics (NPs). Only a few studies tested NPs effects on human health. NPs toxic actions are, in part, mediated by oxidative stress (OS) that, among its effects, affects bone remodeling. This study aimed to assess if NPs influence skeleton remodeling through OS. Murine bone cell cultures (MC3T3-E1 preosteoblasts, MLOY-4 osteocyte-like cells, and RAW264.7 pre-osteoclasts) were used to test the NPs detrimental effects on bone cells. NPs affect cell viability and induce ROS production and apoptosis (by caspase 3/7 activation) in pre-osteoblasts, osteocytes, and pre-osteoclasts. NPs impair the migration capability of pre-osteoblasts and potentiate the osteoclastogenesis of preosteoclasts. NPs affected the expression of genes related to inflammatory and osteoblastogenic pathways in pre-osteoblasts and osteocytes, related to the osteoclastogenic commitment of pre-osteoclasts. A better understanding of the impact of NPs on bone cell activities resulting in vivo in impaired bone turnover could give more information on the possible toxicity consequence of NPs on bone mass and the subsequent public health problems, such as bone disease.

Cannabis suppresses antitumor immunity by inhibiting JAK/STAT signaling in T cells through CNR2

The combination of immune checkpoint blockade (ICB) with chemotherapy significantly improves clinical benefit of cancer treatment. Since chemotherapy is often associated with adverse events, concomitant treatment with drugs managing side effects of chemotherapy is frequently used in the combination therapy. However, whether these ancillary drugs could impede immunotherapy remains unknown. Here, we showed that ^∆9-tetrahydrocannabinol (THC), the key ingredient of drugs approved for the treatment of chemotherapy-caused nausea, reduced the therapeutic effect of PD-1 blockade. The endogenous cannabinoid anandamide (AEA) also impeded antitumor immunity, indicating an immunosuppressive role of the endogenous cannabinoid system (ECS). Consistently, high levels of AEA in the sera were associated with poor overall survival in cancer patients. We further found that cannabinoids impaired the function of tumor-specific T cells through CNR2. Using a knock-in mouse model expressing a FLAG-tagged Cnr2 gene, we discovered that CNR2 binds to JAK1 and inhibits the downstream STAT signaling in T cells. Taken together, our results unveiled a novel mechanism of the ECS-mediated suppression on T-cell immunity against cancer, and suggest that cannabis and cannabinoid drugs should be avoided during immunotherapy.

THE INFLUENCE OF ENDOCANNABINOID SYSTEM ON WOMEN REPRODUCTION

The discovery of the cannabinoid receptors CB₁ and CB₂ in 1990 and 1993, respectively, as well as of the two main endocannabinoids, anandamide in 1992 and 2-arachidonylglycerol in 1995, was an important step in identifying the strongest homeostatic system in the human body, namely the endocannabinoid system. Ever since, research has highlighted the crucial part played by this system in all the reproduction stages: folliculogenesis, spermatogenesis, oogenesis, fecundation, transport of the egg through the fallopian tubes, blastocyte implantation and pregnancy progression, as well as its implications in the physiopathology of the reproductive system: in endometriosis, ectopic pregnancy, miscarriage, preeclampsia, endometrial cancer, polycystic ovary syndrome, ovarian cancer. A special attention must be paid to the phytocannabinoids, natural components originating especially from the Cannabis plant inflorescences, whose medical effects are well-established nowadays with also acting on the receptors of the endocannabinoid system. The most recent research mainly focuses on the reproductive dysfunctions and disorders of the reproductive tissues, respectively, through its action upon the endocannabinoid system. Medical cannabis is nowadays legalized in more and more countries all over the world. At the same time, recreational cannabis remains one of the most consumed drugs (in Romania the most consumed one by young adults). Therefore, it is mandatory for specialists in obstetrics and gynecology, endocrinology, public health, hygiene or for general practitioners, to permanently update their information on this subject.

The anti-inflammatory effect of bacterial short chain fatty acids is partially mediated by endocannabinoids

The endocannabinoid (EC) system has pleiotropic functions in the body. It plays a key role in energy homeostasis and the development of metabolic disorders being a mediator in the relationship between the gut microbiota and host metabolism. In the current study we explore the functional interactions between the endocannabinoid system and the gut microbiome in modulating inflammatory markers. Using data from a 6 week exercise intervention (treatment n = 38 control n = 40) and a cross sectional validation cohort (n = 35), we measured the associations of 2-arachidonoylglycerol (2-AG), anandamide (AEA), N-oleoylethanolamine (OEA) and N-palmitoylethanolamine (PEA) with gut microbiome composition, gut derived metabolites (SCFAs) and inflammatory markers both cross-sectionally and longitudinally. At baseline AEA and OEA were positively associated with alpha diversity (β(SE) = .32 (.06), P = .002; .44 (.04), P < .001) and with SCFA producing bacteria such as Bifidobacterium (2-AG β(SE) = .21 (.10), P < .01; PEA β(SE) = .23 (.08), P < .01), Coprococcus 3 and Faecalibacterium (PEA β(SE) = .29 (.11), P = .01; .25 (.09), P < .01) and negatively associated with Collinsella (AEA β(SE) = -.31 (.12), P = .004). Additionally, we found AEA to be positively associated with SCFA Butyrate (β(SE) = .34 (.15), P = .01). AEA, OEA and PEA all increased significantly with the exercise intervention but remained constant in the control group. Changes in AEA correlated with SCFA butyrate and increases in AEA and PEA correlated with decreases in TNF-ɑ and IL-6 statistically mediating one third of the effect of SCFAs on these cytokines. Our data show that the anti-inflammatory effects of SCFAs are partly mediated by the EC system suggesting that there may be other pathways involved in the modulation of the immune system via the gut microbiome.

Toll-like receptor 2/4 inhibitors can reduce preterm birth in mice

Objectives

Preterm birth (PTB) occurs in 5% to 18% of newborns. However, the underlying inflammatory mechanisms have not been elucidated.

Methods

We established a mouse model of infection-associated PTB. Physical signs in pregnant mice with or without lipopolysaccharide (LPS) treatment were observed, and the frequencies of Toll-like receptor (TLR)2- and TLR4-positive CD11b+ cells were analyzed. Cytokine levels in plasma and pathological changes were assessed following LPS treatment. A rescue experiment was used to probe potential immunologic mechanisms underlying PTB.

Results

Lymphocyte infiltration could be observed in the placentas of mice following intrauterine injection with LPS. The percentage of inflammatory cells decreased 12 hours after treatment. Moreover, TLR2 and TLR4 expression in peripheral blood cells was significantly increased 4 hours after intraperitoneal injection of LPS. Peak TLR2 and TLR4 expression in peripheral blood cells occurred 8 hours post-treatment. TLR4 and TLR-2/4 inhibitors reduced levels of interleukin-10, interferon-γ, and tumor necrosis factor-α in peripheral blood and delayed PTB.

Conclusions

TLR2 and TLR4 inhibition could play important roles in PTB.

Maternal regulation of inflammatory cues is required for induction of preterm birth

Infection-driven inflammation in pregnancy is a major cause of spontaneous preterm birth (PTB). Both systemic infection and bacterial ascension through the vagina/cervix to the amniotic cavity are strongly associated with PTB. However, the contribution of maternal or fetal inflammatory responses in the context of systemic or localized models of infection-driven PTB is not well defined. Here, using intraperitoneal or intraamniotic LPS challenge, we examined the necessity and sufficiency of maternal and fetal Toll-like receptor (TLR) 4 signaling in induction of inflammatory vigor and PTB. Both systemic and local LPS challenge promoted induction of inflammatory pathways in uteroplacental tissues and induced PTB. Restriction of TLR4 expression to the maternal compartment was sufficient for induction of LPS-driven PTB in either systemic or intraamniotic challenge models. In contrast, restriction of TLR4 expression to the fetal compartment failed to induce LPS-driven PTB. Vav1-Cre-mediated genetic deletion of TLR4 suggested a critical role for maternal immune cells in inflammation-driven PTB. Further, passive transfer of WT in vitro-derived macrophages and dendritic cells to TLR4-null gravid females was sufficient to induce an inflammatory response and drive PTB. Cumulatively, these findings highlight the critical role for maternal regulation of inflammatory cues in induction of inflammation-driven parturition.

Evidence for CB2 receptor involvement in LPS-induced reduction of cAMP intracellular levels in uterine explants from pregnant mice: pathophysiological implications

STUDY QUESTION

What is the role of the endocannabinoid system (eCS) on the lipopolysaccharide (LPS) effects on uterine explants from 7-day pregnant mice in a murine model of endotoxin-induced miscarriage?

SUMMARY ANSWER

We found evidence for cannabinoid receptor type2 (CB2) involvement in LPS-induced increased prostaglandin-F2α (PGF2α) synthesis and diminished cyclic adenosine monophosphate (cAMP) intracellular content in uterine explants from early pregnant mice.

WHAT IS KNOWN ALREADY

Genital tract infections by Gram-negative bacteria are a common complication of human pregnancy that results in an increased risk of pregnancy loss. LPS, the main component of the Gram-negative bacterial wall, elicits a strong maternal inflammatory response that results in embryotoxicity and embryo resorption in a murine model endotoxin-induced early pregnancy loss. We have previously shown that the eCS mediates the embryotoxic effects of LPS, mainly via CB1 receptor activation.

STUDY DESIGN, SIZE, DURATION

An in vitro study of mice uterine explants was performed to investigate the eCS in mediating the effects of LPS on PGF2α production and cAMP intracellular content.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Eight to 12-week-old virgin female BALB/c or CD1 (wild-type [WT] or CB1-knockout [CB1-KO]) mice were paired with 8- to 12-week-old BALB/c or CD1 (WT or CB1-KO) males, respectively. On day 7 of pregnancy, BALB/c, CD1 WT or CD1 CB1-KO mice were euthanized, the uteri were excised, implantation sites were removed and the uterine tissues were separated from decidual and embryo tissues. Uterine explants were cultured and exposed for an appropriate amount of time to different pharmacological treatments. The tissues were then collected for cAMP assay and PGF2α content determination by radioimmunoassay.

MAIN RESULTS AND THE ROLE OF CHANCE

In vitro treatment of uteri explants from 7-day pregnant BALB/c or CD1 (WT or CB1-KO) mice with LPS induced an increased production of PGF2α (P < 0.05) and a reduction of the tissue content of cAMP (P < 0.05). These effects were mediated by CB2 receptors since exposure to AM630 (a specific CB2 receptor antagonist) prevented these LPS-induced effects (P < 0.05). Collectively, our results suggest a role for the eCS mediating LPS-induced deleterious effects on reproductive tissues.

LIMITATIONS, REASONS FOR CAUTION

Since our experimental design involves in vitro experiments of uterine explants, the extrapolation of the results presented here to humans is limited.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings provide evidence for the role of CB2 receptors in reproductive events as well as their participation as a mediator of LPS deleterious effects on reproductive tissues.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTEREST(S)

Dr Ana María Franchi was funded by Agencia Nacional para la Promoción Científica y Tecnológica (PICT 2010/0813 and PICT 2013/0097) and by Consejo Nacional de Investigaciones Científicas y Técnicas (PIP 2012/0061). Dr Carlos Davio was funded by Agencia Nacional para la Promoción Científica y Tecnológica (PICT 2013/2050). The authors have no competing interests.

Differential outcomes of TLR2 engagement in inflammation-induced preterm birth

Preterm birth (PTB) is the leading cause of neonatal mortality worldwide. Infection and inflammation are considered main causes of PTB. Among multiple pathogens, Gram‐positive bacteria are commonly linked with induction of PTB. Although activation of innate immune responses, via TLR2 engagement, by Gram‐positive bacteria is a likely cause, whether induction of PTB depends on the potency of specific microbial components to induce Toll‐like receptor (TLR)2‐driven inflammation has not been elucidated. Here, we show that TLR2 activation by synthetic lipopeptides, Pam2Cys, and Pam3Cys specifically, variably influenced inflammation and subsequent induction of PTB. Pam2Cys challenge, compared to Pam3Cys, induced PTB and promoted significantly higher expression of inflammatory cytokines, specifically IL‐6 and IFN‐β, both in vivo and in vitro. Notably, antibody‐mediated neutralization of IL‐6 or genetic deletion of type I IFN receptor (IFNAR) was sufficient to protect from Pam2Cys‐driven PTB and to temper excessive proinflammatory cytokine production. Conversely, IFN‐β or IL‐6 was not sufficient to promote induction of PTB by Pam3Cys. In summary, our data implies a divergent function of TLR2‐activating lipopeptides in the magnitude and type of ligand‐driven inflammatory vigor in induction of PTB.

Targeting Cannabinoid Signaling in the Immune System: "High"-ly Exciting Questions, Possibilities, and Challenges

It is well known that certain active ingredients of the plants of Cannabis genus, i.e., the "phytocannabinoids" [pCBs; e.g., (-)-trans-Δ⁹-tetrahydrocannabinol (THC), (-)-cannabidiol, etc.] can influence a wide array of biological processes, and the human body is able to produce endogenous analogs of these substances ["endocannabinoids" (eCB), e.g., arachidonoylethanolamine (anandamide, AEA), 2-arachidonoylglycerol (2-AG), etc.]. These ligands, together with multiple receptors (e.g., CB₁ and CB₂ cannabinoid receptors, etc.), and a complex enzyme and transporter apparatus involved in the synthesis and degradation of the ligands constitute the endocannabinoid system (ECS), a recently emerging regulator of several physiological processes. The ECS is widely expressed in the human body, including several members of the innate and adaptive immune system, where eCBs, as well as several pCBs were shown to deeply influence immune functions thereby regulating inflammation, autoimmunity, antitumor, as well as antipathogen immune responses, etc. Based on this knowledge, many in vitro and in vivo studies aimed at exploiting the putative therapeutic potential of cannabinoid signaling in inflammation-accompanied diseases (e.g., multiple sclerosis) or in organ transplantation, and to dissect the complex immunological effects of medical and "recreational" marijuana consumption. Thus, the objective of the current article is (i) to summarize the most recent findings of the field; (ii) to highlight the putative therapeutic potential of targeting cannabinoid signaling; (iii) to identify open questions and key challenges; and (iv) to suggest promising future directions for cannabinoid-based drug development.

Type I interferons regulate susceptibility to inflammation-induced preterm birth

Preterm birth (PTB) is a leading worldwide cause of morbidity and mortality in infants. Maternal inflammation induced by microbial infection is a critical predisposing factor for PTB. However, biological processes associated with competency of pathogens, including viruses, to induce PTB or sensitize for secondary bacterial infection-driven PTB are unknown. We show that pathogen/pathogen-associated molecular pattern-driven activation of type I IFN/IFN receptor (IFNAR) was sufficient to prime for systemic and uterine proinflammatory chemokine and cytokine production and induction of PTB. Similarly, treatment with recombinant type I IFNs recapitulated such effects by exacerbating proinflammatory cytokine production and reducing the dose of secondary inflammatory challenge required for induction of PTB. Inflammatory challenge-driven induction of PTB was eliminated by defects in type I IFN, TLR, or IL-6 responsiveness, whereas the sequence of type I IFN sensing by IFNAR on hematopoietic cells was essential for regulation of proinflammatory cytokine production. Importantly, we also show that type I IFN priming effects are conserved from mice to nonhuman primates and humans, and expression of both type I IFNs and proinflammatory cytokines is upregulated in human PTB. Thus, activation of the type I IFN/IFNAR axis in pregnancy primes for inflammation-driven PTB and provides an actionable biomarker and therapeutic target for mitigating PTB risk.

Novel Toll-like receptor-4 antagonist (+)-naloxone protects mice from inflammation-induced preterm birth

Toll-like receptor 4 (TLR4) activation by bacterial infection, or by sterile inflammatory insult is a primary trigger of spontaneous preterm birth. Here we utilize mouse models to investigate the efficacy of a novel small molecule TLR4 antagonist, (+)-naloxone, the non-opioid isomer of the opioid receptor antagonist (−)-naloxone, in infection-associated preterm birth. Treatment with (+)-naloxone prevented preterm delivery and alleviated fetal demise in utero elicited by i.p. LPS administration in late gestation. A similar effect with protection from preterm birth and perinatal death, and partial correction of reduced birth weight and postnatal mortality, was conferred by (+)-naloxone administration after intrauterine administration of heat-killed E. coli. Local induction by E. coli of inflammatory cytokine genes Il1b, Il6, Tnf and Il10 in fetal membranes was suppressed by (+)-naloxone, and cytokine expression in the placenta, and uterine myometrium and decidua, was also attenuated. These data demonstrate that inhibition of TLR4 signaling with the novel TLR4 antagonist (+)-naloxone can suppress the inflammatory cascade of preterm parturition, to prevent preterm birth and perinatal death. Further studies are warranted to investigate the utility of small molecule inhibition of TLR-driven inflammation as a component of strategies for fetal protection and delaying preterm birth in the clinical setting.

Role of the endocannabinoid system in the mechanisms involved in the LPS-induced preterm labor

Prematurity is the leading cause of perinatal morbidity and mortality worldwide. There is a strong causal relationship between infection and preterm births. Intrauterine infection elicits an immune response involving the release of inflammatory mediators like cytokines and prostaglandins (PG) that trigger uterine contractions and parturition events. Anandamide (AEA) is an endogenous ligand for the cannabinoid receptors CB1 and CB2. Similarly to PG, endocannabinoids are implicated in different aspects of reproduction, such as maintenance of pregnancy and parturition. Little is known about the involvement of endocannabinoids on the onset of labor in an infectious milieu. Here, using a mouse model of preterm labor induced by lipopolysaccharide (LPS), we explored changes on the expression of components of endocannabinoid system (ECS). We have also determined whether AEA and CB antagonists alter PG production that induces labor. We observed an increase in uterineN-acylphosphatidylethanolamine-specific phospholipase D expression (NAPE-PLD, the enzyme that synthesizes AEA) upon LPS treatment. Activity of catabolic enzyme fatty acid amide hydrolase (FAAH) did not change significantly. In addition, we also found that LPS modulated uterine cannabinoid receptors expression by downregulatingCb2mRNA levels and upregulating CB1 protein expression. Furthermore, LPS and AEA induced PGF2a augmentation, and this was reversed by antagonizing CB1 receptor. Collectively, our results suggest that ECS may be involved in the mechanism by which infection causes preterm birth.

Endocannabinoid signaling in female reproductive events: a potential therapeutic target?

Nearly 30 years after the discovery in 1964 of the psychoactive ingredient of cannabis (Cannabis sativa), Δ(9)-tetrahydrocannabinol, its endogenous counterparts were discovered and collectively termed endocannabinoids (eCBs): N-arachidonoylethanolamine (anandamide) in 1992 and 2-arachidonoylglycerol in 1995. Since then, intense research has identified additional eCBs and an ensemble of proteins that bind, synthesize and degrade them, the so-called eCB system. Altogether, these new compounds have been recognized as key mediators of several aspects of human pathophysiology, and in particular of female fertility. Here, the main features of the eCB system are presented, in order to put in a better perspective the relevance of eCB signaling in virtually all steps of human reproduction and to highlight emerging hopes that elements of this system might indeed become novel targets to combat fertility problems.

Genetic Manipulation of the Endocannabinoid System

The physiological and pathophysiological functions of the endocannabinoid system have been studied extensively using transgenic and targeted knockout mouse models. The first gene deletions of the cannabinoid CB(1) receptor were described in the late 1990s, soon followed by CB(2) and FAAH mutations in early 2000. These mouse models helped to elucidate the fundamental role of endocannabinoids as retrograde transmitters in the CNS and in the discovery of many unexpected endocannabinoid functions, for example, in the skin, bone and liver. We now have knockout mouse models for almost every receptor and enzyme of the endocannabinoid system. Conditional mutant mice were mostly developed for the CB(1) receptor, which is widely expressed on many different neurons, astrocytes and microglia, as well as on many cells outside the CNS. These mouse strains include "floxed" CB(1) alleles and mice with a conditional re-expression of CB(1). The availability of these mice made it possible to decipher the function of CB(1) in specific neuronal circuits and cell populations or to discriminate between central and peripheral effects. Many of the genetic mouse models were also used in combination with viral expression systems. The purpose of this review is to provide a comprehensive overview of the existing genetic models and to summarize some of the most important discoveries that were made with these animals.

Interleukin-10: a pleiotropic regulator in pregnancy

Pregnancy is a unique and well-choreographed physiological process that involves intricate interplay of inflammatory and anti-inflammatory milieu, hormonal changes, and cellular and molecular events at the maternal-fetal interface. IL-10 is a pregnancy compatible cytokine that plays a vital role in maintaining immune tolerance. A wide array of cell types including both immune and non-immune cells secret IL-10 in an autocrine and paracrine manner. IL-10 binds to a specific receptor complex and activates JAK-STAT and PI3K-Akt signaling pathways while inhibiting NF-κB signaling pathway. IL-10 exerts its anti-inflammatory effects mainly by decreasing pro-inflammatory cytokines such as IL-1, IL-6, IL-12, and TNF-α, by inducing heme oxygenase-1, and by inhibiting antigen presentation via blocking major histocompatibility complex (MHC) class II expression. Prior studies from our group and others have shown that IL-10 also functions as a potent protector against vascular dysfunction, and enhancement of IL-10 may serve as an immunotherapeutic intervention to treat adverse pregnancy outcomes. This review seeks to critically evaluate the archetypal functions of IL-10 as an immune suppressive factor as well as its novel functions as a vascular protector and modulator of endoplasmic reticulum (ER) stress and autophagy in the context of normal and adverse pregnancy outcomes.